Motor-control system.



H. L. BEACH.

MOTOR CONTROL SYSTEM.

APPLICATION HLED AUG-6, 915.

1,242,910. Patented Oct. 16, 1917.

FILE; mvsrqma Haw/arc! 1;. fieirach UNITED STATES PATENT OFFICE.

HOWARD I1. BEACH, OF EDGEWOOD PARK, PENNSYLVANIA, ASSIGNOR TO WESTING-HOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENN- SYLVANIA.

MOTOR-CONTROL SYSTEM.

Specification of Letters Patent.

Patented Oct. 16, 1917.

Application filed August 6, 1915. Serial No. 43,994.

To all whom it may concern:

Be it known that I, HOWARD L. BEACH, a citizen of the United States, anda resident of Edgewood Park, in the county of Allegheny and StateotPennsylva'nia, have invented 'a' new and useful Improvement inMotor-Control Systems, of which the following is a specification.

My invention relates to motor-control systems, and it has for its objectto provide a simple and efiective means for controlling the speed ofelectric motors during their acceleration, operation and retardation.

Motor-control systems of the same general character as that of myinvention have, heretofore, been provided with series and shuntcontrolling circuits which comprised resistors to be so controlled as tovary the speed of the motors between desired limits. In sucharrangements, it has been necessary to provide switching mechanisms of asomewhat complicated nature to control the re 'sistors. It has beencustomary, also to decrease the resistance of either of the controllingcircuits by shunting the resistors injcluded therein.

In accordance with the present invention, I provide a plurality ofresistors which are connected in shunt relation to the motor armature.The usual series or starting resistor'is controlled by acceleratingswitches in the usual manner. By means of a simple arrangement, theshunt resistors are successively transferred from the shunt circuit to aseries connection iii-parallel with the starting resistor. The effect isto gradually increase the resistance of the shunt circuit and todecrease the resistance in series with the armature, winding. Byproperly arranging the several circuits, the speed of the motor may becontrolled as desired and the motor may be 'causedto operate uniformlyat relatively low speeds.

In the accompanying drawings, Figure 1. is a diagrammatic view ofcircuits and apparatus embodying my invention. Fig. 2 is a diagrammaticview of a schematic arrangement of the system of Fig. 1. Figs. 3, 4, 5,6 and 7 arediagrammatic views illustrating the circuits as arrangedinaccordance with successive positions of the controller.

Line conductors l and, 2, which may be connected to any suitable sourceof direct current, supply energy to an electric motor having an armaturewinding 3 and a shunt field winding 4. A shunt circuit for the armaturewinding comprises resistors 5, 6 and 7 which are adapted to be connectedin parallel with each other. The connections of the resistors 5, 6 and 7are respectively controlled by electromagnetic switches 8, 9 and 1G,each of which is provided with a shunt actuating coil 11.

A sectional starting resistor 12, which is in series with the motorarmature, is controlled by a series of progressively actuated switches13, 14 and 1 The switch 18 is provided with a shunt actuating coil 16while the switches 1 1 and 15 are provided with series actuating coils17. Each of the switches for controlling the resistor 12 is providedwith series holding coils 18, each of which, except that of switch 15,is in series with the actuating coil 17 of the succeeding switch toclose.

A controller 19, or master switch, comprises a contact segment 20 whichsuccessively engages a plurality of contact members 21 for producing theoperation of the several electromagnetic switches in their propersequence, as will be later described.

To start the motor, a line switch 22 is first closed. The controllerhandle is then actuated to the left, as viewed in Fig. 1, to engage thefirst contact member 21 ancl thereby complete a circuit comprising theactuating coil 28 or" a main switch 24. The latter then closes tocomplete the armature circuit for the mot-or which extends from thepositive line conductor 2 through line switch 22, main switch 24,armature winding 3, starting resistor 12, and main switch 22 tolineconductor 1. A low-resistance shunt circuit for the armature winding3 comprises the resistors 5, 6 and 7 which are connected in parallelwith each other. The electrical con nections that are established by thecontroller in its first position are diagrammatically shown in Fig. 3.The motor then operates at a low rate of speed, because of thelow-resistance shunt circuit for the armature.

In the second position of the controller, the coil 11 of theelectromagnetic switch 8 is energized to actuate the latter to its upperposition and thereby disconnect the resistor 5 from the shunt circuitand connect it in series with the armature winding 3 but in parallelwith the resistor 12. The several circuits are now arranged inaccordance with the diagram of Fig. a. The removal of the resistor 5from the shunt circuit operates, in effect, to. increase the resistanceof the shunt circuitand thereby cause an increasedcurrent to traversethe motor winding. The connection of the resistor in parallel with theresistor 12 serves to decrease the resist ance of the series circuit andthereby accelerate the motor.

The actuation of the controller to its third and fourth positionsoperates, in ya similar manner, as successively transfer the resistors 6and 7 from the. shunt circuit to the series. circuit, the resistors Sand7 being connected in parallel with the resistors 12 and and witheachother. The circuits ob taining ii the respective positions of thecontroller 19 are illustrated in Figs. 5 and (3. The resistance of theshunt circuit is gradually increased, and the resistance of theseriescircuit is gradually decreased, by the changes in connections abovedescribed, andthe motor speed is increased to a corresponding degree.

The actuation of the controller arm 19 to its final position completes acircuit for the actuating coil 16 of switch 13. The latter then closestocomplete a circuit through the holding-coil 18 and the actuating coil.17 of switch 11 for shunting one of the sections of the resistor 12. Theswitches 11 and 15 then close in order to complete a shunt circuit forthe resistor 12 and thereby further accelerate the motor to its normal,speed. The shunting of the resistor 12 operates to establish a shunt,circuit for the resistors 5, (tand 7,

When it is .desired to reduce the speed of the motor, the controllerhandle may be actuated in theopposite direction to thatpreviouslydescribed and, allowed to remain at any. intermediateposition. It will he, noted that the resistor 12 is shunted during theoperation ofthe motor, since the holding coil 18 of switch 15 is inseries with the motor armature- The return of the controller arm towardits illustrated or inoperative position will not operate to inserttheresistor 12 in series with the motor armature until the main switch 24is opened to break the circuit of the coil 18.

hen the controller arm is in its third position, the circuit of theactuating coil v11 of the switchlO has been opened, and the latter,assumesits illustrated position to disconnect the resistor 7 from theseries circuit and connect it in parallel with themotor armature. Thecounter-electromotive force of the motor thencauses current to traversethe shunt circuit thus established, andthe speed of the motor isaccordingly decreased. In a similar. manner,.when.the controller isactuated to its second and first positions, the resistors. 6 and 5 aresuccessively transferred from theseries circuit to the shunt circuit andare again connected in parallel with each other. The reduction ofresistance in the shunt circuit causes an increased current to. traverseit, and the speed of the motor is reduced in a corresponding degree.

hen the shunt circuit comprises the resistors 5, 6 and 7 connected inparallel with each other, the motor operates uniformly at acomparatively low rate of speed. This condition is especially desirablein connection with hoists, elevators and similar ma chines in which itis. desirable tooperate. at a low rate of speed; before the motor isbrought toa stop. Tostop the motor, when it isoperating under theconditions just described, it is only necessary to return thecontroller-to its off position. The motor then operates as a generator,and. current traverses the shunt circuit comprising the resistors 5, Gand 7 to efiect the dynamic r k n of the mice To bring the DIQtOI'QHlQklY to rest when it is operating at a comparatively highrate ofspeed, the controller handle may be returned to its olf position,through the various, intermediate positions, to succes; sively connecttheresistorsfi, 6 and 7 in-,the sh uit circuit-and to open the mainswitch 24, The dynamic braking action, which is thereby produced, may hegraduated byad j usting the controller in accordance with the motorspeeghorthe maximum effect maybe obtained by returning the controller toits .ofl'? positioutoreduce the resistance of the dynamic brakingcircuit to a minimum.

In the operation of the system as above described, itwill :be noted thatthe circuits of the shunt-connected;resistors are not merely opened .toincrease the resistance of;the shunt circuit, hutare transferred bodilyfrornpne circnitto another by. means ofI double-threw switches. By;means of the arrangement above described, I am enabled to graduallyaccelerate thespeed; of the motor and to cause the latter to ouerate atvariousspeeds corresponding to the arrangement of the er ral, ir uits- 1tml i h r nab ed to bring themotor safely and gradually to rest u nta-si m s ixw p y a y: namic braking action, the eftect of which is withinthecontrol of the operatorv WYhile, the n otone nbodied in the controlsystem has been shown and described asheserating .inone direction. only,it will beo ews tha the P in ipl o 1 my nt n is qu l y. pr ca ele a m ep v de with reyersing meanssuch as. is commonlye131,- ployed inconnection with; eleyators, hoists and similarmachines. It isunderstood, that such changes maybe made, without depart, ing from,thespirit of my invention, as .fall within thescope ofi-the appendedclaims,

I claim .as my invention 1.,- In a motor-controlsystem, the combinationwith an electric motor, and a pin, {Q0

rality of resistors in parallel relation to the armature of said motor,of means for successively connecting said resistors in series relationto the motor armature and in parallel relation to each other.

2. In a motor-control system, the combination with an electric motor,and a plurality of resistors in parallel relation to the armature ofsaid motor and in parallel relation to each other, of means forsuccessively connecting said resistors in series relation to saidarmature and in parallel relation to each other.

3. In a motor-control system, the combination with a shunt-woundelectric motor, a resistor in series relation to the motor armature, anda second resistor in parallel relation to said armature and in seriesrelation to the other resistor, of means for successively connecting thesecond resistor in series with the motor armature and in parallelrelation to the other resistor and shunting said other resistor.

4. In a motor-control system, the combination with a shunt-woundelectric motor and a resistor, of means operable, according to itsposition, to connect said resistor either in parallel or in seriesrelation to the armature of said motor, and means for controlling saidconnecting means.

5. In a motor-control system, the combination with an electric motor,and two circuits that are respectively in series and in parallelrelation to the armature of said motor and in series relation to eachother, of a resistor, and means for transferring said resistor from onecircuit to the other.

6. In a motor-control system, the combination with a shunt-woundelectric motor, and two circuits that are respectively in series and inparallel relation to the armature of said motor, of a resistor in eachof said circuits, and means for successively transferring one of saidresistors from the one circuit to the other in parallel relation to theother resistor and shunting said other resistor.

7. In a motor-control system, the combination with an electric motorhaving an armature and a field-magnet winding, and two circuits that arerespectively in series and in parallel relation to said armature and inseries relation to each other, of a resistor in each of said circuits,and means for controlling one of said resistors whereby it istransferred to the other circuit in parallel relation to the otherresistor.

8. In a motor-control system, the combination with an electric motor, aresistor in series relation to the armature of said motor, a pluralityof resistors in parallel relation to said motor armature and to eachother, of means for successively connecting each of saidparallel-connected resistors in parallel relation to saidseries-connected resistor.

9. In a motor-control system, the combination with an electric motor, aresistor in series relation to the armature of said motor, a pluralityof resistors in parallel relation to said motor armature and to eachother, of means for successively connecting each of saidparallel-connected resistors in parallel relation to saidseries-connected resistor and for shunting said series-connectedresistor.

In testimony whereof, I have hereunto subscribed my name this 21st dayof July,

- HOWARD L. BEACH.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents,

Washington, D. C.

